1. Technical Field
The present invention relates to methods for making coaxial cables and, particularly, to a method for making a carbon nanotube based coaxial cable.
2. Discussion of Related Art
Coaxial cables are used as carriers to transfer electrical power and signals. A conventional coaxial cable includes a core, an insulating layer, and a shielding layer, usually surrounded by a sheathing layer. The core includes at least one conducting wire. The conducting wire can be, e.g., a solid or braided wire, and the shielding layer can, for example, be a wound foil, a woven tape, or a braid. However, as for the conducting wire made of a metal, a skin effect will occur in the conducting wire. The skin effect can make the effective cross-section of the current flows reduce, thus the effective resistance of the cable becomes larger, and cause signal decay in the process of transmission. Further, the conducting wire and the shielding layer made of metal has less strength for its size, so must be comparatively greater in weight and diameter. Thus, the coaxial cables have problems being used in the fields, such as ultra-fine cable, space, or space equipment.
Conventional method for making the cable includes the following steps of: coating a polymer on an outer surface of the at least one wire to form an insulating layer; applying a plurality of metal wire or braided metal wire on the insulating layer to form a shielding layer; and covering a sheathing layer on the shielding layer.
Carbon nanotubes (CNTs) are a novel carbonaceous material and received a great deal of interest since the early 1990s. Carbon nanotubes have interesting and potentially useful heat conducting, electrical conducting, and mechanical properties. A conducting wire made by a mixture of carbon nanotubes and metal has been developed. However, the carbon nanotubes in the conducting wire are disorderly. Thus, the skin effect is not eliminated. Further, the method for making the coaxial cable having carbon nanotubes is executed by mixing a small amount of carbon nanotubes with a metal by means of vacuum melting, vacuum sintering or vacuum hot pressing. The method is complicated.
What is needed, therefore, is a method for making a coaxial cable, the method is simple, low-cost and suitable for mass production, and the coaxial cable has good conductivity, high mechanical performance, light quality and small diameter.
Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate at least one embodiment of the present coaxial cable and method for making the same, in at least one form, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.